(a) Field of the Invention
The present invention relates to a photo-sensitive resin composition and a protective film for printed circuit board, particularly to a photo-sensitive resin composition and a protective film for printed circuit board having superior heat resistant and mechanical property.
(b) Description of the Related Art
As electronic devices are miniaturized and become lightweight, a photo-sensitive protective film which can form minute open patterns is being used in a printed circuit board (hereinafter PCB), a semiconductor package board, a flexible printed circuit board (FPCB), and the like.
The protective film is also called ‘solder resist’, and the characteristics of developing property, high resolution, insulating property, resistance to soldering heat, tolerance to gold plating, and the like are required. Particularly, for example, a crack-resistant property against a temperature cycle test (TCT) from 55° C. to 125° C., or highly accelerated stress test (HAST) property to fine wirings, in addition to said characteristics are required to the solder resist for package board.
Recently, a Dry Film Solder Resist (DFSR) superior in uniformity of film thickness, surface smoothness, and thin-film-forming property receives attention as the solder resist. Such DFSR can give the effects of simplification of resist-forming process, or reduction of solvent displacement in the resist-forming process, in addition to said characteristics.
The protective film for PCB must satisfy various properties such as high thermal stability, mechanical property, chemical resistance, hygroscopic property, and the like.
Generally, if the composition has a recipe for improving the mechanical property, the heat-resistant falls down, and if the composition has a recipe for improving the heat-resistant, the mechanical property falls down, and thus it has been demanded to develop the composition superior in both of the mechanical property and the heat-resistant.
Japanese Patent Publication No. 2008-189803 discloses a photo-curable and thermo-curable resin composition comprising (A) a carboxyl-containing photo-sensitive resin obtained by reacting a polybasic acid anhydride (c) on a reaction product of a polynuclear epoxy compound (a) and an unsaturated group-containing monocarboxylic acid (b), (B) a carboxyl-containing urethane (meth)acrylate compound, (C) a photo-polymerization initiator, (D) a thermosetting component having two or more cyclic ether groups and/or cyclic thioether groups in one molecule, and (E) a diluent.
Japanese Patent Publication No. 2007-310380 discloses a photo-sensitive resin composition comprising (a) a binder polymer having carboxyl groups, (b) a photo-polymerizable monomer having at least one ethylenically unsaturated group, (c) a polyurethane compound, and (d) a photo-polymerization initiator, wherein the polyurethane compound (c) is obtained by reacting an epoxy acrylate compound having two or more hydroxyl groups and an ethylenically unsaturated group with a diisocyanate compound and a diol compound having a carboxyl group.
Japanese Patent Publication No. 2008-250305 discloses a solder resist containing an acid-modified vinyl ester which is synthesized from an epoxy compound, a phenol compound, an unsaturated monobasic acid, and a polybasic acid anhydride, while using a crystalline epoxy resin having a melting point of 90° C. or more as at least a part of the epoxy compound and using a compound having a bisphenol S skeleton as at least a part of the phenol compound.
However, said methods still do not satisfy the heat-resistant and the mechanical property at the same time, and it is required to develop new technology.